The present invention relates to a semiconductor laser (or semiconductor device), and more specifically to a semiconductor laser and array having equilateral triangle optical resonators with output wave guide.
Optical resonators are essential components of lasers, and light feedback and optical coherent intensifying effect take place in the resonator. Resonators of various structures may be applied for providing the feedback, e.g., Fabry-Perot resonator formed by parallel plane mirrors, distributive feedback Bragg resonator causing light feedback by periodical variations of refractive index or gain, and the microdisk structure having total reflection Whispering gallery mode etc. Recently, we discover that single mode lasing can be easily realized in an equilateral triangle micro-resonator, and the equilateral triangle resonator may be directly connected to a waveguide to acquire light output. The lasers with an equilateral triangle resonator shall be suited for a light source of integrated optics and a micro semiconductor laser having orienting output. In view of the above, on April and September, 2000, we applied the China patents xe2x80x9cphotoelectric device having equilateral triangle micro optical resonatorsxe2x80x9d (application Ser. No.: 00105875.4) and xe2x80x9csurface emission laser with equilateral triangle resonatorsxe2x80x9d (application Ser. No.: 00123775.6). And the papers xe2x80x9cmode frequencies and quality factors calculated for equilateral triangular optical resonators by FDTD technique and Pade approximation,xe2x80x9d IEEE Photonics Technology Letters, vol. 12, pp 813-815, July 2000, xe2x80x9cinfluence of output waveguide on mode quality factor in semiconductor microlasers with an equilateral triangle resonator,xe2x80x9d Applied Physics Letters, vol. 77, pp. 3511-3513, November 2000, and xe2x80x9canalysis and numerical simulation of eigenmode characteristics for semiconductor lasers with an equilateral triangle micro-resonator,xe2x80x9d IEEE J. Quantum Electronics, vol. 37, pp. 100-107, January 2000, have been published. In the triangle resonator, optical field intensity of fundamental mode is rather weak in the three corners of triangle resonator, and high quality factor can still be guaranteed for the resonant mode of triangle resonator when an output waveguide is connected to the corner of resonator to acquire orienting light output. For a two-dimensional equilateral triangle resonator with side length 5 xcexcm and refractive index 3.2, our numerical simulation implies that quality factor of the fundamental mode at the wavelength of about 1.5 xcexcm can exceed 15,000, while when an output waveguide with width of 0.4 xcexcm is connected to a vertex of the resonator, the quality factor of the fundamental mode remains to surpass 1500, which is more than the quality factor of a 300-xcexcm-length Fabry-Perot resonator with cleaved mirrors. In the semiconductors, such as InP etc., the incline making an angle of 45xc2x0 with the wafer surface can be obtained by wet chemical etching, that is xe2x80x9cchemical etching of InGaAsP/InP DH wafer,xe2x80x9d J. Electrochem. Soc: Solid-State Science and Technology, vol. 129, no. 5, pp. 1053-1062, May, 1982). Thus, if the output waveguide of equilateral triangle optical resonator intersects with the aligned incline making an angle of 45xc2x0 with the wafer surface, surface emission semiconductor laser with the equilateral triangle optical resonator can be realized. An incline making an angle of 45xc2x0 with the wafer surface can also be acquired by dry etching technique by placing the semiconductor wafer at an inclined angle.
Employing an array of equilateral triangle micro-resonators with various sizes, a multi-wavelength semiconductor laser array can be formed, if the output waveguide is perpendicular to an incline making an angle of 45xc2x0 with the wafer surface, then a surface emission multi-wavelength semiconductor laser array can be obtained. The output waveguides of the equilateral triangle micro-resonators having various sizes are collected to the same output waveguide, then a multi-wavelength semiconductor laser can be formed. When the output waveguide serving as an optical amplifier, the output power of the equilateral triangle micro resonator semiconductor lasers can be further enhanced.
An object of the invention is to provide an edge and surface emission semiconductor laser and array having the equilateral triangle micro optical resonators. The edge emission semiconductor laser and array have the output waveguide connected to the equilateral triangle resonators, and the surface emission semiconductor laser and array have an incline making an angle of 45xc2x0 or 135xc2x0 with the wafer surface and being perpendicular intersection with the output waveguide.
The main conception of this invention is to introduce a waveguide connected to one of the vertices of a triangle resonator, and further enables the output waveguide of the triangle resonator to be intersected with the aligned incline making an angle of 45xc2x0 or 135xc2x0 with the surface, to realize the edge and surface emission semiconductor laser and array of orienting output. By connecting the triangle resonators of various sizes to the same output waveguide, a semiconductor laser of multi-wavelength output is obtained. If the substrate is transparent to the emitting wavelength, e.g. InP substrate to 1.3 and 1.5 xcexcm, surface emission laser light may be output from the growth surface or substrate; if the substrate is non-transparent to the emission wavelength, then a unthreaded hole should be etched on the substrate for the laser output from substrate side, or the incline of swallow-tailed mesa can be prepared by dry etching enabling the surface emission laser light to be output from the growth surface.
Mass production of the semiconductor laser and array having equilateral triangle resonator and orienting output may apply planar technology, and the surface emission semiconductor laser and array having equilateral triangle resonators can be fabricated using a conventional epitaxial wafer of the conventional edge emission semiconductor laser.
An object of the invention is realized by the following technical scheme:
The edge emission and surface emission semiconductor laser and array have equilateral triangle micro-resonators and output waveguides, which are an edge emission semiconductor laser having equilateral triangle resonator with output waveguide, and a surface emission semiconductor laser with equilateral triangle resonator having output waveguide and an incline deflecting output light by 90xc2x0. The structure comprises a slab waveguide composed of the lower cladding layer, active layer and upper cladding layer, the semiconductor material may be various active materials, e.g., InGaAsP, AlGaAs GaAs, InGaN, InGaAsN etc., and the corresponding materials of cladding layers. The active material may be bulk, quantum well, quantum wire, and quantum dot semiconductor materials. Employing quantum dot material can reduce the influence of nonradiative combination in etched surface. Wherein an external region of the equilateral triangle employs dry or wet etching technique to etch to the lower cladding layer or the substrate, while unetched equilateral triangle region serves as a resonator. The triangular sides are used as reflecting mirrors, and the vertices of the triangle or side are connected or coupled to the output waveguide for realizing directional emission. In case of the output waveguide be intersected with the cleavage plane or the orthogonal etched surface, and the cleavage plane coated with antireflecting film, then a conventional edge emission semiconductor laser having a triangular micro resonator can be produced; while the output light is deflected by 90xc2x0 if the output waveguide is intersected with an incline, then a surface emission semiconductor laser having a triangle micro resonator can be made, likewise, its output end face should be coated with an antireflection film to reduce the influence of light feedback. The output waveguide may be an optical amplifier to enhance the output power. If the material is grown on (111) substrate, then the equilateral triangle resonator might be easily obtained by wet chemical etching.
The semiconductor laser array or multi-wavelength semiconductor laser array having equilateral triangle resonator may be formed by the lasers having the equilateral triangle resonators of the same or different sizes.